1. Field of the Invention
The present invention relates to a silicone ladder polymer coating composition.
2. Description of the Background Art
In recent years, the pattern of a highly integrated semiconductor device has been increasingly refined and densified. In order to form a passivation layer, a stress relaxation film or an insulating layer for a solid state component, a method of rotation-coating a polymeric material having smaller residual stress, superior smoothness and higher purity as compared with an inorganic material at 0.5 to 30 .mu.m has been studied. Such a polymeric material is prepared from silicone ladder polymer or polyimide resin. When the silicone ladder polymer is applied to a passivation layer, a stress relaxation film or an insulating layer for a solid state component, it is necessary to rotation-coat a silicone ladder polymer solution onto a surface of a substrate of Si, Si-O, SiN or Al, dry the same, and finely work the as obtained polymer film for forming a ventilation part for upper and lower conductor layers and a through hole for connection with an external lead wire, and the like. Application of lithography is required for such a method. In a conceivable process, for example, a positive resist material of cresol novolak is applied onto the polymer film which has been rotation-coated and dried, and a prescribed pattern is formed on the resist film. Then the silicone ladder polymer film is etched and the resist film is removed, and heat curing is performed for film formation. In this case, the silicone ladder polymer film is etched and the resist film is removed in wet-type steps, and hence the silicone ladder polymer film is exposed to a developing solution for the resist material, a rinsing solution, an etching solution for the silicone ladder polymer film, a removing solution for the resist film, and the like. Japanese Patent Laying-Open No. 55-94955 (1980) and Japanese Patent Publication No. 63-14749 (1988) discloses silicone ladder polymer coating solutions.
When a silicone ladder polymer film which is formed of such a conventional polymer coating composition is finely worked by lithography, stress is applied to respective ones of two-layer polymer films upon dipping in solutions in respective steps, by solvent storaging or the like. Thus, the polymer films are easily separated from a substrate. This problem is particularly remarkable in a thick silicone ladder polymer film. Further, the conventional coating solution, which contains a hygroscopic polar solvent as well as a polymeric surface active agent, is so inferior in preservation stability that the as-formed film tends to be whitened.